Generally, masking effect is based on a psychoacoustic theory. Since small-scale signals neighbor to a large-scale signal are blocked by the large-scale signal, the masking effect utilizes the characteristic that a human auditory system is not good at recognizing them. As the masking effect is used, data may be partially lost in encoding an audio signal.
However, it is not enough for a decoder of a related art to compensate for a loss signal attributed to masking and quantization.